In the field of industrial automation the use of robotic manipulators, such as for example motorized articulated arms, which can be combined with tools intended to act on pieces to be manipulated or processed, is known. Depending on requirements, the tool can thus be a clamp for gripping objects to be manipulated, a pair of pincers, a punch, etc.
In many cases, manipulators are designed to mount interchangeable tools. In this case, connecting devices for the functional connection of each tool to the respective manipulator are generally used.
In general terms, today available connecting devices comprise a body intended to be permanently fixed to the manipulator, for example by screws. The body of the device comprises in turn a plurality of seats for housing corresponding coupling portions of the tool, for example holes for housing pins or clutches of the tool. The device further comprises an engaging mechanism to engage the coupling portions of the tool; this mechanism is movable between a locked position, at which the coupling portions of the tool are locked in the respective seats of the body and cannot disengage therefrom, and an unlocked position, at which the coupling portions of the tool are free to be taken out from the respective seats.
In practice, the connecting device is fixed to the manipulator and the tool can be removably coupled to the body of the device.
Depending on the type of tool to be used, the functional connection to be implemented by the connecting devices may also include electrical, pneumatic, hydraulic connections, etc., for feeding the tool.
Not only must the connecting devices guarantee the proper tool-manipulator functional coupling but they also must allow the tool to be replaced in a way as quick and safe as possible for the inspection staff of the workstation which comprises the manipulator.
For example, in the molding field of plastic manufactured articles, manipulators for gripping, handling and repositioning pieces and/or molds or parts of them are used. The interchangeable tools combined with manipulators generally consist of pneumatically operated clamps.
A typical connecting device broadly used in this and other areas of interest and defining de facto a standard respected by manufacturers, comprises a substantially toroidal body, fixed to the manipulator, equipped with seats for housing corresponding interlocking pins provided on a plate fixed to the tools. The seats are arranged circumferentially around the axis of the body. In a position radially inward with respect to the housing seats, the body comprises a plurality of ducts for feeding compressed air used to operate the tools each time constrained to the device; along these ducts automatic valves for opening and closing the ducts themselves are usually installed. The engaging mechanism to engage the tool pins is a circular lock ring provided with through openings each consisting of a substantially circular hole joined to an eyelet whose width is less than the diameter of the circular hole. The lock ring is coaxial with the body and is superimposed thereto so that each through opening intercepts a corresponding housing seat. The lock ring can be manually rotated between a first unlocked angular position, at which the circular holes are aligned with the accommodating seats and the tool pins can be inserted into or taken out from the respective seats respectively for constraining or disengaging the tool to/from the device, and a second locked angular position, at which the eyelets are aligned with the accommodating seats and lock the tool pins at a section thereof having reduced diameter, so as to prevent the tool from disengaging from the connecting device.
In practice when a tool needs to be replaced, the operator acts on the engaging mechanism, i.e. he/she rotates the lock ring to move the relative holes into alignment with the accommodating seats of the pins of the tool mounted on the device. In this way, the tool can be separated from the device and thus from the manipulator, so as to leave space for another tool. The automatic valves are kept open by the tool that presses against them while still constrained to the connecting device. When the tool is physically separated from the device, the automatic valves act to close the feed of compressed air in the respective ducts.
A prior art device is described in US 2008/0042432. A set of connecting devices according to the known art is also commercialized by the Applicant under the name of “cambia-utensile automatico per robot QC-Series” (“automatic tool-replacer for QC-Series robots”).
An important drawback of the described connecting devices lies in the fact that the automatic valves act too late in closing the feeding of compressed air when the tool is separated from the device. In practice, even when the operator moves the lock ring to the unlocked position to release the tool, the compressed air continues to be fed and is sufficient to keep the same tool active, for example is sufficient to keep open the jaws of a pneumatic clamp. Only after the tool has been separated from the device, the residual compressed air in the tool inevitably is discharged in the atmosphere and usually causes the tool to be disabled. Referring again to the example of the pneumatic clamp, the jaws close all at once, evidently putting at risk the safety of the operator handling the tool.
Workers may be injured even seriously by some tools. Even if the tool is activated by means of pneumatic vacuum, rather than by compressed air, the same drawback can be found. In this case, as a result of the separation of the tool from the connecting device, the pressure in the tool itself is immediately recovered and the latter is instantaneously disabled.
Another drawback of conventional solutions is that the compressed air fed to the connecting device can apply a thrust counteracting the coupling, or the detachment, of the tool to/from the device itself. The greater the number of ducts supplied with compressed air, the more apparent this circumstance.
Therefore, the Applicant proposed the solution described in the Italian Patent IT 1413748 (Application No. 102012902091284, ex BS2012A000145) and marketed under the name QCX, QCX90-A to QCX200-A series; it is a connecting device comprising:
a) a body, fixable to a manipulator, provided with one or more seats for accommodating corresponding coupling portions of a tool, for example holes for accommodating corresponding interlocking pins of the tool;
b) one or more ducts for feeding or suctioning a working fluid to/from the tool, for example compressed air or vacuum, wherein the ducts pass through at least part of the device body;
c) an engaging mechanism to engage the coupling portions of the tool, wherein the engaging mechanism can be activated for locking and unlocking the coupling portions of the tool respectively in/from the corresponding accommodating seats of the device body;
d) closing means to close the feeding/suctioning ducts, mounted in or on the device body, wherein said closing means are designed to automatically close the feeding/suctioning ducts before the engaging mechanism, once activated, unlocks the tool from the device.
The closing means are independent from the tool, meaning that the activation of the closing means does not necessarily depend on whether the tool is present on the device or not.
Preferably, the working fluid is compressed air, but alternatively it can also be oil, pneumatic vacuum, etc.
The above mentioned characteristic d) is very important for safety at workplaces, as it allows the prevention of injury of the operator employed in replacing the tools each time combined with the device. Since the closing means are always activated adequately in advance with respect to the engaging mechanism moving to the unlocked position of the tool, the rapid decompression (if the working fluid is compressed air) or pressurization (if the tool is activated by pneumatic vacuum) of the tool, usually occurring at the separation from the traditional connecting devices, is thus prevented.
In other words, thanks to closing means automatically activated by the engaging mechanism when the engaging mechanism is moved to the unlocked position, the tool, as it is separated from the connecting device for the replacement with another tool, can be prevented from being undesirably activated or disabled. The benefits for the safety of workers are obvious.
The closing means function as a tap which, if necessary, stops the flow rate of the working fluid, fed or suctioned, upstream of the tool.
Being able to stop feeding the working fluid gives the further advantage that the working fluid cannot impede the coupling or the detachment of the tool to/from the device, as is the case in traditional solutions using compressed air, as described above.
Referring again, for simplicity, to the example previously made in which the connecting devices are used to support pneumatic clamps, the closing means of the feeding ducts are operable to stop feeding compressed air before the clamp is separated from the device itself. This prevents compressed air from building up in the tool before the latter is actually separated from the device. As a result, the tool does not depressurize all at once and therefore the jaws do not snap close, or open (depending on the case), when the operator handles the clamp.
The activation of the engaging mechanism is kinematically contingent on the activation of the closing means, meaning that these components are designed to interact in such a way that the closing means intervene to close the feeding of working fluid before the tool can be disconnected from the device.
Although the device according to the Italian patent IT 1413748 achieved an excellent result, the Applicant found that there is still room for the improvement thereof. In particular, the connecting device described in IT 1413748 provides two separate handles for operating the closing means and the engaging mechanism, respectively, these handles being referred to with numerals 82 and 72 in the drawings, although users are accustomed to use only one of them. Moreover, the presence of the two handles 72 and 82, which in turn control the circular lock ring 7 and the plate 8, causes the axial dimension of the device to be slightly greater than solutions without a system for closing the pneumatic lines, whereas users want the overall dimensions of the device to be kept as small as possible.